Two-sheet detector



TWO-SHEET DETECTOR Filed April 24, 1937 INVENTOR Augusi' CSmifh "*7 w m Z/ M ZM Patented Jan. 3, 1939 UNITED PATENT O-FFlfCE Apblicationfipfifi24, 1937; Serial No. 138-,807

. 6 Claims.

This invention relates to printing presses "and in particular, to-meansfor'stopping the feeding of blank sheets to the press in casemore than 'one sheet'is simultaneously 'picke'dt'up from f the 5 pile at the'feeding end.

The feeding'of more thanone'sheetat a time to high-speed presses causes a great'dealof difficulty even after'the, press has beenstopped'by automatic throw-out means operable in response to the feeding of two sheets, for-"example. It is'the object of my invention, therefore, to provide means for preventing the usual-"sheet feeding means from'feeding a plurality ofsheets-to the press at a time, whereby to avoid-'this-"difliculty.

In accordance-with my invention, "I providea relatively fixed abutment past which the 'sheets being fed to the; press are 'moved. "A movable member adapted tocooperate with the fixed abutment is moved towardthe latter duringa porti'on of the passage of 7 each sheet therepast; defining a gap through which a'sin'gle'sheet "willpass freely. 'The fixed abutment is-preferably adjustable so thatthe'precise spacing-between it-and the movable-member may be obtained, depending upon the thickness of the sheets being handled. If "two sheets should-be "fed-simultaneously they are gripped =between"the"fixed abutment and movable'member" and prevented from being'fed forward to the'press. 1 The'press is then automatically thrown out by known means, operated on failure of'thedelivery mechanism to advance a sheet at the'proper time.

A clear understanding of the invention may be gained from the following detailed description thereof, which is to be readdn conntection with the accompanying drawing illustrating a present preferred embodiment. In the drawing Figure 1 is a View largely diagrammatic,show ing partly in side elevation and partly in section, the various elements comprisingtheinvention; and

Figure 2 is a fragmentaryview to a large-scale showing a portion of the apparatusillust'rated in Figure l.

As indicated in outline in FigureLsheets are adapted to be lifted from a pile F "supported on a delivery table I I by suction feet (not shown) and when so lifted, transferred laterally of the pile by transfer suckers [2, for delivery to the press. The movement of the transfer suckers is indicated by the dotted line-showing of the alternate position thereof. The detailsofthe feed table and the sheet lifting and "transfer mechanism are well known and thusdonot require further explanation.

A shaft or'supportingbarl3-'extends between the usual side frames of the press and supports a downwardlyeXtendi-ng bracket l4. A spring finger l5 issecured to the lower end of the bracket by screws I6. The position of the free screw ll-is'provldedwith a lock nut Hi to hold it in'a'djusted position. 7

"The'presserfootfl is mounted on the upper end of'a thrust rod 20. The finger l5 and pressure foot 19 "form 'a pair ofgripper jaws or .ca-lipersbetween which the sheets are passed and which; as hereinafter pointed out are yieldingly moved toward each 'other'with suflicient force to seize'and'arrest thefeedingmovement of the sheets in casetwopr more sheets are simultaneously passed-between them. The rod 20 is slidablet'hrough agguide bearingZl carried on a bracket-22 secured'toverticalguide bars'23 formingpart of thefeed table. The guide-bearing 2i :ispositionedsothat on vertical movement of theiro'd 20the foot *l9 approaches the finger l5 and is disposed in about the same vertical plane :asthe latter.

The rod 201s" urged upward by 'a compression 'springf lt'disposed'between the (guide bearing .2! andaset collar "25 on the rod 20. A stop 25a :limits upward movement "of the rod.

. A'cam lever 2B"is tiltable on a shaft 2'! mounted inany-eonvenienttmanner'in the press frame. Iherright hand end of the lever 26 is provided With*a-clevis*28"having 'a tapped bore adapted to'receive the lower threaded end'-29' of the rod 20. A"lobk"nut3ll securesthe rod in adjusted position "relative to the clevis.

Thedefthanden'd'of the lever 26 is provided with afollowenroller 3| cooperating with a cam 32. "The cam is keyed to a shaft 33'journaled'in thefpressframe-and driven by any convenient 'meansin synchronism with the operation of the 'press"and,"therefore; the sheetfeeding means it. The cam 32 has a recessed portion 34 covering about of its periphery. The remainder'of the cam'has'a substantially uniform'radius. The position of the 'cam on the shaft 33 and the speed of rotation of the-latter are determined so that the cam lever 26 will effect a complete tilting cycle each time a' sheet is fedfrom the pile iii to thepress, and preferably the cam is so positioned'that the recess 34- thereof will engage the roller 3| shortly after the sheet being fed has advanced past the finger I 5.

In the operation of the apparatus, the finger I5'is firstadjusted by turning the screw if so that when the foot I9 is in its uppermost position (shown in Figures 1 and 2), the space therebetWEEIl WiII 'freely'pass a single sheet from the pile T0. The tadjustment is madecloseenough, howevenso that should .two sheets be lifted and 'fe'dsimultaneously from the pile, the foot i9, because of the double thickness thereof, will press them against the finger I5 tightly enough to lift it therefrom for engagement by the transfer suckers l2. Shortly after the latter havemoved the leading edge of the sheet beyond the finger I5, the cam 32 permits the spring to shift the lever 26 and raise the rod 20 and the foot [9 to the illustrated position. If only onesheet has been lifted from the pile and fed forward therefrom, it will pass freely between the finger and the foot and continue to move with the suckersl2. After a relatively short period, the rotation of the cam 32 restores the leverv 26 to its normal position and depresses the rod 20 and the foot 19 against the force of the spring 24. This leaves ample space between the finger l5 and the foot I9 for the free passage of the sheet without any drag or restraining effect whatever thereon. As a matter of fact, there is only very little or no restraint placed upon the sheet when the foot is in its uppermost position.

If two sheets should simultaneously be lifted from the pile, the double thickness thereof will cause the foot I9 on reaching the upper extremity of its movement, to press the sheets firmly against the finger l5 with the result that forward movement thereof is arrested and the transfer suckers l2 slide off the leading edge. The successive feed of sheets being thus interrupted, the automatic means for throwing-out the press comes into play and the press is immediately stopped.

It will be recognized that the removal of two sheets from between the finger l5 and the foot I9 is a relatively simple matter so that the press can be restarted with very little delay. This is not true if the two sheets are permitted to reach the press and be fed thereinto. The advantages of the invention from the standpoint of the avoidance of time loss resulting from the accidental lifting and feeding of two sheets instead of one will be readily recognized. The invention,

furthermore, is simple and inexpensive in construction so that it adds verylittle to the cost of construction or maintenance of the press.

Although I have illustrated and describedbut one preferred embodiment of the invention, it will be understood that changes in the construction disclosed may be made without departing from the spirit of the invention or the scope of the appended claims.

I claim:

1. In a sheet-feeding apparatus, the combination with means for releasably seizing a sheet from a pile and moving it to a point laterally thereof, of a relatively fixed abutment adjacent the path of the sheet, a presser foot adapted to cooperate with said abutment and effective therewith to grip and restrain a plurality of sheets against feeding movement should they be seized and moved simultaneously, and means operating during the passage of each sheetpast the presser foot for moving the foot into a gripping position relative to said abutment such that the movement of a plurality of sheets is arrested.

2. In a sheet-feeding mechanism, means for feeding sheets from a pile, grippers between which the fed sheets are. passed, normally so separated as to permit free passage of the sheets between them, adjustable means for limiting the movement of the grippers toward each other to leave a gap between them greater than the thickness. of one sheet but less than that of two sheets, and means operating as a sheet is fed past the grippers for moving the grippers toward each other with sufficient force to seize a plurality of sheets and arrest their feeding movement should they be fed simultaneously.

3. In a sheet feeding-mechanism, means for feeding sheets from a pile, grippers between which the fed sheets are passed, normally so separated as to permit free passage of the sheets between them, adjustable means for limiting the movement of the grippers toward each other to leave a gap between them greater than the thickness of one sheet but less than that of two sheets, and yielding means operating after the leading edge of a sheet has been fed past the grippers for urging the grippers toward each other with suflicient force to seize a plurality of sheets and arrest their feeding movement should they be fed simultaneously.

4. In a sheet-feeding mechanism, means for feeding sheets from a pile, grippers between which the fed sheets are passed, normally so separated as to permit free passage of the sheets between them and having a limited movement toward each other to leave a predetermined gap between them only wide enough to permit the passage of but a single thickness sheet between the grippers, and means for moving the grippers toward each other after the leading edge of a sheet has passed the grippers and for then separating them before the trailing edge of the sheet reaches the grippers, said means acting to move the grippers together with sufficient force to clamp and hold against feeding movement two or more sheets fed together in multiple thickness. 7 5. In a sheet-feeding mechanism, means for feeding the sheets, grippers between which the fed sheets are passed normally so separated as to permit free passage of the sheets between them, means for limiting the movement of the grippers toward each other to leave a gap of predetermined width between them, and means operating periodically as the sheets are fed past the grippers for moving the grippers toward each other with suflicient force to seize and arrest the feeding movement of the sheets should the thickness thereof exceed the gap setting of the grippers.

6. In a sheet-feeding mechanism, means including a transfer sucker for lifting the top sheet from a pile and moving it laterally, a relatively fixed gripper jaw past which the sheets are successively fed, a movable gripper jaw cooperating therewith, a stop for limiting the movement of the movable jaw to leave a gap between the jaws suflicient for the passage of a single sheet only, a spring for urgingthe jaws together with sufficient force to grip and hold a plural thickness of sheets against the lateral feeding movement, and means for holding the jaws apart against the force of the spring when the leading edge of a sheet is fed past the jaws, for then allowing the spring to move the jaws together to permit a single sheet to be fed but to hold a plural thickness of sheets against movement until the transfer sucker has moved beyond the held sheets, and for thereafter again holding the jaws apart as the trailing edge of a fed sheet passes between them.

AUGUST C. SMITH. 

